Maine’s alewife population has seen a dramatic resurgence, with annual migration counts in some river systems rising from fewer than 800 fish three decades ago to millions today. This recovery, driven by large-scale dam removals and the installation of specialized fish passage infrastructure, has restored a critical "biological conveyor belt" of nutrients between the Atlantic Ocean and inland freshwater habitats.
The alewife (Alosa pseudoharengus), often referred to as river herring, is a small, silver-scaled fish that plays a vital role in local ecosystems. Each spring, adult alewives migrate from the Atlantic Ocean into Maine’s rivers, traveling up to 100 miles inland to spawn in ponds and lakes. This migration cycle provides a foundational food source for a wide range of predators, including bald eagles, ospreys, seals, and various species of trout and pollock. The Passamaquoddy people historically recognized this importance, naming the species siqonomeq, which translates to “the fish that feeds all.”
Restoring Migration Through Dam Removal and Engineering
For centuries, the construction of dams along Maine’s waterways created impassable barriers that effectively blocked alewives from their historic spawning grounds. While some colonial-era dams included rudimentary chutes, they were often insufficient to sustain fish populations. By the mid-20th century, the combination of habitat fragmentation and intensive commercial harvesting had caused alewife numbers to collapse. According to figures from the ASMFC, the nationwide catch of river herring averaged approximately 170 million pounds per year during the 1950s, a level that proved unsustainable.
In response, the state of Maine began a decades-long effort to reopen river systems. The removal of two dams on the Penobscot River, a project spanning from 1999 to 2016, is widely cited by conservationists as a premier success story in fish restoration. Where full dam removal is not feasible, municipalities have turned to engineering solutions. In Benton, a hydroelectric dam was retrofitted in 2006 with a “fish elevator”—a system that uses artificial currents to lure alewives into buckets, which then lift the fish over the barrier, allowing them to continue their journey upstream.
Smaller-scale projects have also proven effective. In Phippsburg, the town replaced an inefficient 1980s-era fish channel with a rock-pool system in 2025. This design mimics natural stream conditions, helping fish navigate elevation changes. According to the Maine Department of Marine Resources (DMR), these restoration efforts are bolstered by a “secret sauce”: the intentional stocking of alewives in targeted ponds five years before a new fishway project is completed. This ensures that the next generation of fish returns to the newly accessible spawning grounds.
Economic Impact and Sustainable Harvesting
As of 2024, 25 Maine municipalities have received approval to conduct local commercial harvests, according to DMR records. This represents a significant shift from the 2012 moratorium imposed by the ASMFC, which halted all commercial river herring fishing on the Atlantic coast until states could provide evidence of sustainable management plans.
This rigorous oversight ensures that enough fish reach spawning grounds to maintain population stability. In 2024, Maine’s local commercial catches totaled 2.5 million pounds, a figure that remains tightly regulated compared to historical industrial-scale fishing.
Challenges and Future Outlook
Despite the success in Maine, the broader Atlantic coast outlook remains complex. While Maine’s populations are rebounding—with an estimated 20 million alewives counted in 2025—other states are not experiencing the same trend. Scientists are currently investigating why populations elsewhere are struggling, with potential factors including ocean-based fishing pressure, changing water temperatures, and climate-driven droughts. Last summer, for example, drought conditions in Maine resulted in notable die-offs of alewife spawn, highlighting the vulnerability of the species to environmental shifts.
Funding remains a critical component of ongoing restoration efforts. The 2022 Bipartisan Infrastructure Law and the Inflation Reduction Act provided over $60 million to support 23 public-private fish passage projects across the state, according to federal records. As these infrastructure projects continue, the DMR maintains a list of future sites slated for restoration. With aging dams becoming increasingly expensive to maintain, many communities are finding that removing barriers or installing modern fishways is a more viable long-term strategy for both the environment and the municipal budget.
Residents and conservationists interested in the status of local runs can track updates through the Maine Department of Marine Resources or the Gulf of Maine River Herring Network.